Regensburg 1998 – scientific programme

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TT: Tiefe Temperaturen

TT 4: Niedrigdimensionale Systeme, Magnetotransport und Quantenhalleffekt

TT 4.3: Talk

Monday, March 23, 1998, 15:15–15:30, H 19

Charge Fluctuations in Quantum Point Contacts and Chaotic Cavities in the Presence of Transport — •M. H. Pedersen¹, M. Büttiker¹, and S. A. van Langen² — ¹Département de Physique Théorique, Université de Genève, 1211 Genève 4, Switzerland — ²Instituut-Lorentz, Leiden University, P.O. Box 9506, 2300 RA Leiden, The Netherlands

We analyze the frequency-dependent current fluctuations induced into a gate near a quantum point contact or a quantum chaotic cavity. We use a current and charge conserving, effective scattering approach in which interactions are treated in random phase approximation. The current fluctuations measured at a nearby gate, coupled capacitively to the conductor, are determined by the screened charge fluctuations of the conductor. Both the equilibrium and the non-equilibrium current noise at the gate can be expressed with the help of resistances which are related to the charge dynamics on the conductor. We evaluate these resistances for a point contact and determine their distributions for an ensemble of chaotic cavities. For a quantum point contact these resistances exhibit pronounced oscillations with the opening of new channels. For a chaotic cavity coupled to one channel point contacts the charge relaxation resistance shows a broad distribution between 1/4 and 1/2 of a resistance quantum. The non-equilibrium resistance exhibits a broad distribution between zero and 1/4 of a resistance quantum.